He is a New Zealand-born British chemist and physicist whobecame known as the father of nuclearphysics. In early work he discovered theconcept of radioactive half-life, provedthat radioactivity involved thetransmutation of one chemical element toanother, and also differentiated andnamed alpha and beta radiation, provingthat the former wasessentially helium ions. This work wasdone at McGill University in Canada. It isthe basis for the Nobel Prize inChemistry he was awarded in 1908 "forhis investigations into the disintegrationof the elements, and the chemistry ofradioactive substances"
In 1911, Rutherford and hiscoworkers discovered that thealpha particles were helium atomswith their electrons removed.They were positive and verymassive compared to the electron.
They focused a stream of high-speed alpha particles on a thin gold foiland observed how they would be scattered after passing through the foil. Fig. 1: Rutherfords experiment
If Thomson’s model was correct, the alphaparticles with their high-speed and heavy masswould all pass through the gold foil largelyundeflected. To their surprise, they observed that, in fact,most of the particles went straight through butthere were a few that were scattered at wideangles and there were some, although fewer still,that were deflected by very large angles, andsome occasional ones which practically bouncedback to the source.
Based on these observations, theydismissed Thomson’s raisin breadmodel and proposed the ff:The fact that most alpha particles were able to go through the foil implies that the gold atoms in the foil must be empty space.An atom has a core that is very small.The negatively charged electrons move around the nucleus and occupy most of the volume of the atom.
He was a Danish physicist who madefoundational contributions tounderstanding atomic structure and quantummechanics, for which he received the NobelPrize in Physics in 1922.Bohr mentored andcollaborated with many of the top physicistsof the century at his institute in Copenhagen.He was part of a team of physicists workingon the Manhattan Project. Bohr marriedMargrethe Nørlund in 1912, and one of theirsons, Aage Bohr, grew up to be an importantphysicist who in 1975 also received the NobelPrize. Bohr has been described as one of themost influential scientists of the 20th century.
In view of Rutherford’s model, he assumed that the prevailing laws of physics at that time were not sufficient to describe the atom. He proposed that the electrons move in orbits around the nucleus but only orbits of certain radii, corresponding to certain definite energies, are permitted. An electron in a permitted orbit has a specific energy and is said to be in an ‘allowed’ energy state. An electron in an allowed energy state will not radiate energy and therefore will not be spiral to the nucleus.
Was born in Denmark, on November 13, 1959)is a Danish physicist. In 1999, she led a HarvardUniversity team who, by use of a superfluid,succeeded in slowing a beam of light to about17 metres per second, and, in 2001, was able tomomentarily stop a beam.In 1989, Hau accepted a two-year appointmentas a postdoctoral fellow at Harvard University.She received her degree from the University ofAarhus in Denmark in 1991. Her formalizedtraining is in theoretical physics but her interestmoved to experimental research in an effort tocreate a new form of matter known as a Bose-Einstein condensate. In 1991 she joined theRowland Institute for Science at Cambridge as ascientific staff member. Since 1999 she has heldthe Gordon McKay Professor of Applied Physicsand Professor of Physics at Harvard. She now isthe Mallinckrodt Professor of Physics andApplied Physics at Harvard.
Dr. Hau’s scientific and service contributions have been recognized throughhonors that include: the MacArthur Fellow 2001–2006; the NKT award, awarded by the Danish Physical Society, 2001; the Ole Rømer Medal, awarded by the president of the University of Copenhagen, 2001; an Honorary Degree, Æreshåndværker Kjøbenhavns Håndværkerforening, awarded in the presence of Her Majesty, Queen Margrethe II of Denmark, Copenhagen, 2001; recipient of the Samuel Friedman Rescue Award, awarded by the Friedman Foundation, University of California, Los Angeles, 2001; recipient of the Year 2000 Award from the Top Danmark Foundation, Copenhagen Denmark, 2000; recipient of the J. C. Jacobsen 200 Year Anniversary Award, awarded by the Carlsberg Foundation, Denmark, 1989; recipient of the Research Fellowship, 1986–1989, awarded by the Faculty of Sciences, University of Aarhus, Denmark.Dr. Hau recently was awarded an honorary appointment to the Royal DanishAcademy of Sciences and Letters and was elected a foreign member of theRoyal Swedish Academy of Sciences in 2008.She received in 2010 Danes Worldwides annual awards "ÅretsVerdensdansker" [Best World Dane] because she, according to DanesWorldwide emphatically and persistently has put Denmark on the world map.